This invention relates to a seam and a method for forming the seam to join pieces of synthetic turf material together. In another aspect, this invention relates to an improved seam and method for forming it whereby synthetic turf materials, having a polymeric backing, are joined together. In yet another aspect, this invention relates to a seam and method for forming the seam which is exceptionally strong and wear-resistant in outdoor installations.
In recent years, synthetic turf materials have been widely used to cover athletic fields, parade grounds, playgrounds, highway medians, areas surrounding swimming pools, patios, and the like. Such synthetic turf materials normally simulate a well manicured, natural grass surface in that the synthetic turf material is made up of a multitude of upstanding ribbon-like fibers that are secured to a base or a substrate. Such fibers, as nylon, polypropylene, polyvinyl chloride and the like, have been widely used as the material for forming the upstanding grass leaf-like ribbons. Because of the durability of such materials of construction, it is possible to produce a simulated grass surface, or a synthetic turf material that stands up well under extremely harsh conditions. Such durable surfaces are now widely used for the surfaces of athletic playing fields and the like, wherein the synthetic turf is exposed to the grinding, abrasive, and twisting forces, caused by the shoes of athletes, animals, and the like, as they walk or run across the surface of the synthetic turf.
With the development of synthetic turf materials in recent years, the strength and durability properties of the synthetic turf materials have been improved to a point where such turf materials stand up well under even the most extreme wear conditions out of doors. One particularly troublesome problem does plague the synthetic turf industry in that the synthetic turf materials are manufactured in long continuous rolls of material and it is necessary to join the materials together for final installation. The installation of synthetic turf material is some way resembles the installation of carpet material in that the synthetic turf material is unrolled, cut to the desired sizes, and the adjacent pieces of synthetic turf material are brought together by some manner and means. Many different techniques have been utilized for the installation of synthetic turf materials. One widely accepted method for joining synthetic turf materials together, along the sides and edges of the turf material, has been to simply glue or adhere the individual pieces of the turf material to a solid base or substrate, such as a wood, concrete, asphalt, or other substrate. Such a method of installation is grossly inadequate in those instances where a pad or cushion layer must be disposed between the synthetic turf material and the relatively rigid and firm substrate. Even in those instances where there is no necessity for installing a pad or layer of cushioning material between the synthetic turf material and the rigid base, problems have still developed in that the seam or the area along the abutting edges of adjacent pieces of the synthetic turf material is very difficult to seal and water, dirt, and other materials invariably migrate into the seam. Over prolonged periods of time, such water and dirt will cause a destruction of a portion of the seam by means of the water and other material creeping along minute crevices, cracks, or holes between the base of the synthetic turf material and the supporting wood, concrete, asphalt, etc., anchor structure.
The problems of forming a long lasting durable seam between adjacent pieces of synthetic turf material become more acute when a pad or a layer of cushioning material is disposed between the synthetic turf material and the firm supporting structure. In those instances, it is virtually impossible to form a seam between the adjacent pieces of the synthetic turf material that will resist wear from the users, as well as the ravages of rain, sleet, snow, sunlight and the like. Various techniques have been utilized to form seams between synthetic turf materials that are applied over a pad or layer of cushioning material. Such techniques include a conventional sewing technique wherein the adjacent pieces of the turf material are actually sewn together, usually from the back. Such a procedure is extremely tedious and time consuming and often times, affects the overall appearance of the installed synthetic turf material. The sewing technique further produces localized stress points around the points where the thread or yarn is passed through the synthetic turf material. Overall, such a sewing technique has not been widely accepted in the installation of synthetic turf materials.
Another technique that has been utilized for the installation of synthetic turf materials utilizes a heat sealing technique wherein some type of a tape material is positioned beneath the abutted edges of the synthetic turf material to be seamed. By application of heat to the surface of the tape and the bottom portion of the abutted seams, the temperature can be raised to a point where at least a portion of the surface of the tape or the lower portion of the abutted seams will soften and become tacky. Thereafter, by the application of pressure to compress the lower portion of the abutted edges with the surface of the tape material, some fusion or adhesion will take place to thereby form a bond between the abutted edges of the synthetic turf material and the surface of the heat sealing tape. This technique has been widely used but has been found grossly unacceptable because it is extremely difficult to heat the materials to the precise softening point without damage to the surface of the synthetic turf material. The problems connected with heating the heat sealing tape are compounded in that most installations of synthetic turf are made outdoors and under varying temperature conditions. The resulting seams are non-uniform and have a high degree of failure, especially in outdoor use on athletic fields.
Still another technique that has been utilized to join the abutted edges of synthetic turf material together is by application of various types of glue, mastic material and adhesive material. While this particular technique is widely used, it has certain inadequacies in that most seams produced with such glues, mastics, or adhesives will fail when they are subjected to use and to the elements, such as rain, snow, sleet, sunlight and temperature changes. Even the widely acclaimed epoxy type cements fail under normal usage because of temperature changes and water seeping into various voids and other cracks in the epoxy cement layer will gradually weaken and deteriorate the bond.
It is, therefore, apparent that there is a need for an improved seam and method for forming the seam between the abutted edges of synthetic turf material. It is also apparent that there is a need for a seam and method for installing it that can be quickly and easily installed under field conditions and maintain its strength over long periods of use and exposure to the elements.